A composite impeller and a low specific speed non-overloading centrifugal pump

Abstract

The present invention relates to the technical field of impeller structures of low specific speed non-overloading centrifugal pumps, and particularly relates to a composite impeller and a low specific speed non-overloading centrifugal pump, which comprise an impeller rear cover plate and blades. The blades are uniformly arranged on the disk surface of the impeller rear cover plate around its own axis. A forked opening is arranged at a position from 1 / 5 to 1 / 4 of the length from the inlet end to the outlet end of the blade, and the forked opening divides the outlet end of the blade into at least two forked blades; the wrap angle of the blade on the disk surface of the impeller rear cover plate is 150° to 170°, and the outlet angle of the blade on the disk surface of the impeller rear cover plate is 15° to 19°. The present invention can improve the operation performance of the impeller, reduce the casting difficulty of the impeller, reduce the weight of the casting, and reduce the material cost.

Description

Technical Field

[0001] The present invention relates to the technical field of impeller structures of low specific speed non-overloading centrifugal pumps, and particularly to a composite impeller and a low specific speed non-overloading centrifugal pump. Background Art

[0002] The impeller is a key component in a centrifugal pump, and its function is to directly transfer mechanical energy to the liquid to increase the static pressure energy and dynamic pressure energy of the liquid.

[0003] In existing low specific speed fire-fighting centrifugal pumps, especially for non-overloading pumps with a specific speed less than 60, in order to obtain non-overloading power characteristics, as Figure 1 shown, the outlet angle of the blades on the impeller on the impeller cover plate is designed to be relatively small, usually between 11° and 13°. Due to the small outlet angle, the flow direction of the water flow in the impeller will deviate more from the axis of the impeller, and thus a larger wrap angle is required to guide the water flow. Usually, the angle of the wrap angle is above 200° to ensure that the water flow can smoothly pass through the impeller and generate a higher lift at the rated flow rate. After the flow rate at the high-efficiency point, as the flow rate increases, the head drops rapidly, so that the power has a maximum value, which conforms to the characteristics of a non-overloading pump. At the same time, the thickness of the blades at the inlet and outlet of the existing impeller is relatively large, resulting in a small outlet width of the impeller, which makes the casting of the impeller difficult and the casting rejection rate high.

[0004] In existing low specific speed centrifugal pumps, as Figure 2 shown, the outlet angle of the blades on the impeller on the impeller cover plate is very large, usually above 28°. Due to the large outlet angle, the wrap angle will be relatively small, usually below 120°. Adding auxiliary blades near the blade outlet is beneficial to reducing the diffusion loss of the fluid in the blade outlet area. The outlet angle of this pump is very large, and the flow rate and head at the rated point of the pump will be very high, and the efficiency will also be appropriately improved. However, as the flow rate increases, the power rises faster than the efficiency increases, and the power cannot meet the requirements of non-overloading characteristics. Therefore, it cannot be used for fire-fighting certification with non-overloading characteristics. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a composite impeller and a low specific speed non-overloading centrifugal pump, which can improve the operation performance of the impeller and reduce the casting difficulty of the impeller.

[0006] To solve the above technical problem, the technical solution adopted by the present invention is: a composite impeller, including an impeller rear cover plate and blades. The blades are evenly arranged around the axis of the impeller rear cover plate on the disk surface of the impeller rear cover plate. A forked opening is provided at a position from 1 / 5 to 1 / 4 of the length from the inlet end to the outlet end of the blade, and the forked opening divides the outlet end of the blade into at least two forked blades;

[0007] The included angle of the blade on the disk surface of the rear cover plate of the impeller is 150° to 170°, and the outlet angle of the blade on the disk surface of the rear cover plate of the impeller is 15° to 19°.

[0008] To solve the above technical problems, another technical solution adopted by the present invention is:

[0009] A low specific speed non-overloading centrifugal pump includes a pump body and the composite impeller in the above solution disposed inside the pump body.

[0010] The beneficial effects of the present invention are as follows: Different from the prior art, a forking port is provided at a position from 1 / 5 to 1 / 4 of the length from the inlet end to the outlet end of the blade. During use, the fluid between adjacent blades, that is, the fluid normally entering from the inlet of the composite impeller, will be output under the action of the blade. Part of the reflux fluid will enter the forking port, and the forking blade applies force to the fluid in the forking port and then outputs the fluid. In this way, the flow rate and head output by the composite impeller are ensured. Furthermore, when the usage requirements are met, the outlet angle of the blade on the impeller cover plate can be increased, thereby reducing the included angle of the blade on the impeller cover plate. At the same time, the forking port provided on the blade reduces the thickness of the blade, and the weight of the impeller is reduced by more than 15%. Description of the Drawings

[0011] Figure 1 Schematic cross-sectional structure of an existing impeller Figure 1 ;

[0012] Figure 2 Schematic cross-sectional structure of an existing impeller Figure 2 ;

[0013] Figure 3 Schematic cross-sectional structure diagram of a composite impeller proposed by the present invention;

[0014] Figure 4 Schematic structure diagram of a composite impeller proposed by the present invention;

[0015] Figure 5 Schematic cross-sectional structure diagram of a low specific speed non-overloading centrifugal pump provided by the present invention;

[0016] Figure 6 Outlet pressure waveform image of the pump body of an existing impeller in the pumplinx computational fluid dynamics software;

[0017] Figure 7 Outlet pressure waveform image of the pump body of a composite impeller proposed by the present invention in the pumplinx computational fluid dynamics software;

[0018] Figure 8 Impeller power waveform image of an existing impeller in the pumplinx computational fluid dynamics software;

[0019] Figure 9 The power waveform image of an impeller in the Pumplinx computational fluid dynamics software for a composite impeller proposed by the present invention;

[0020] Label description:

[0021] 1. Rear shroud of the impeller;

[0022] 2. Blade; 21. Forking opening;

[0023] 3. Forked blade;

[0024] 4. Front shroud of the impeller; 41. Casting exhaust port;

[0025] 5. Pump body. Specific implementation manner

[0026] To describe in detail the technical content, achieved objectives and effects of the present invention, the following is described in conjunction with the implementation manners and with reference to the accompanying drawings.

[0027] It should be noted that, in the following text, the inlet end of the blade 2 is the end of the blade 2 away from the edge of the rear shroud 1 of the impeller, and the outlet end of the blade 2 or the outlet end of the forked blade 3 is the end of the blade 2 or the forked blade 3 facing the edge of the rear shroud 1 of the impeller.

[0028] Please refer to Figures 3 to 5 As shown, a low specific speed non-overloading centrifugal pump of the present invention includes a rear shroud 1 of the impeller and blades 2. The blades 2 are evenly arranged on the disk surface of the rear shroud 1 of the impeller around its own axis. A forking opening 21 is arranged at a position from 1 / 5 to 1 / 4 of the length from the inlet end of the blade 2 to the outlet end of the blade 2. The forking opening 21 divides the outlet end of the blade 2 into at least two forked blades 3;

[0029] The included angle of the blade 2 on the disk surface of the rear shroud 1 of the impeller is B, and the outlet angle of the blade 2 on the disk surface of the rear shroud 1 of the impeller is A. Among them, preferably, B is 150°, 155°, 160°, 165°, 170°, and A is 15°, 16°, 17°, 18°, 19°.

[0030] Working principle: During use, the low specific speed non-overloading centrifugal pump drives the rear cover plate 1 of the impeller to rotate through a prime mover. The water body located between adjacent blades 2, that is, the water body that normally enters from the inlet of the compound impeller, will be output under the action of the blades 2. Part of the falling-back water body will enter the bifurcation port 21, and the bifurcated blades 3 will apply force to the water body in the bifurcation port 21 and then output the water body. In this way, the flow rate and head output by the compound impeller are ensured. Furthermore, when the usage requirements are met, the outlet angle A of the blade 2 on the rear cover plate 1 of the impeller can be increased, thereby reducing the angle of the wrap angle B of the blade 2 on the rear cover plate 1 of the impeller. At the same time, the setting of the bifurcation port 21 on the blade 2 reduces the thickness of the blade 2 and reduces the overall mass.

[0031] It should be noted that for the existing impeller structure as Figure 2 shown, the bifurcated blades 3 are arranged at the position from 2 / 3 to 3 / 4 of the length from the inlet end to the outlet end of the blade 2 in order to reduce the fluid diffusion loss between the blades 2. The effective flow channel area between the blades 2 in this structure does not decrease, and the inlet area of the flow channel between the blades 2 is smaller than the outlet area. The blade does work on the fluid, and the fluid flows from the inlet end of the blade 2 to the outlet end of the blade 2, and the static pressure energy continuously increases. As the flow rate exceeds the efficient point flow rate, the head of the impeller decreases slowly, the efficiency drops rapidly, and the power will increase rapidly. Therefore, the non-overloading characteristic cannot be obtained.

[0032] As Figure 3 shown, the bifurcated blades 3 arranged at the position from 1 / 5 to 1 / 4 of the length from the inlet end to the outlet end of the blade 2 greatly reduce the effective flow channel area between the blades 2, and the flow channel area between the blades 2 is much smaller than that of the existing impeller in Figure 2 . The inlet area of the flow channel between the blades 2 is larger than the outlet area. The blade 2 does work on the fluid, and the fluid flows from the inlet end of the blade 2 to the outlet end of the blade 2. The converted static pressure energy is lost, and the greater the flow rate, the greater this static pressure energy loss. As the flow rate exceeds the efficient point flow rate, the head can decrease rapidly, the efficiency also decreases, the power will reach a maximum value, and as the flow rate continues to increase, the power will decrease. This meets the requirements of the non-overloading characteristic.

[0033] Furthermore, the thickness of the inlet end of the blade 2 is 2.2 mm to 2.5 mm, and the thickness of the outlet end of the bifurcated blade 3 is 3.8 mm to 4.3 mm. Among them, the preferred thickness of the inlet end of the blade 2 is 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, and the thickness of the outlet end of the bifurcated blade 3 is 3.8 mm, 3.9 mm, 4 mm, 4.1 mm, 4.2 mm.

[0034] As can be seen from the above description, by limiting the inlet end of the blade 2 and the thickness of the outlet end of the bifurcated blade 3, the influence of cavitation on the blade 2 and the bifurcated blade 3 is reduced under the condition of meeting the use strength.

[0035] Please refer to Figure 3 As shown, further, 4 to 6 blades 2 are evenly arranged on the disk surface of the rear cover plate 1 of the impeller around its own axis.

[0036] As can be seen from the above description, when the centrifugal pump meets the usage requirements of low specific speed without overload, it can reduce the flow resistance and ensure the efficiency of the low specific speed non-overloading centrifugal pump.

[0037] Please refer to Figure 4 As shown, further, the composite impeller further includes a front cover plate 4 of the impeller, and the front cover plate 4 of the impeller covers the blade 2.

[0038] As can be seen from the above description, the setting of the front cover plate 4 of the impeller can protect the blade 2.

[0039] Please refer to Figure 4 As shown, further, a casting exhaust port 41 is provided on the front cover plate 4 of the impeller.

[0040] As can be seen from the above description, the casting exhaust port 41 can facilitate the discharge of the gas generated during casting during the process of integrally forming the composite impeller by casting, so as to ensure the blank shape of the composite impeller.

[0041] Please refer to Figure 4 As shown, further, the casting exhaust port 41 is arranged on the front cover plate 4 of the impeller along the bifurcation port 21, and the bifurcated blade 3 does not pass directly below the casting exhaust port 41.

[0042] As can be seen from the above description, during the later processing, the welder only needs to weld the casting exhaust port 41, the bifurcated blade 3, and the front cover plate 4 of the impeller, and then process the impeller according to the requirements of the drawing after welding. Since the welding area of the casting exhaust port 41 is small and the deformation caused by welding is small, the overall strength can be ensured to be high.

[0043] In a control experiment, in comparison with the existing impeller in Figure 1 , when the outer diameter of the impeller, the impeller outlet width, the number of blades, and the material selection of the existing impeller and the composite impeller are the same, the outlet angle A of the existing impeller is 11°, the blade thickness at the inlet of the existing impeller reaches 4 mm, and the blade thickness at the outlet of the existing impeller reaches 10 mm; for the composite impeller to reach the same flow rate and head as the existing impeller, the outlet angle A of the composite impeller is 17°, the thickness of the blade 2 at the inlet of the composite impeller reaches 2.3 mm, and the thickness of the bifurcated blade 3 at the outlet of the composite impeller reaches 4 mm. It can be clearly seen that the designed outlet angle A of the composite impeller is larger than the outlet angle A of the existing impeller, so that the angle of the wrap angle B of the blade 2 on the rear cover plate 1 of the impeller can be reduced. And the thicknesses of the blade 2 and the bifurcated blade 3 at the inlet and outlet of the composite impeller are both smaller than the thicknesses of the corresponding positions of the blades of the existing impeller, which not only reduces the influence of cavitation, but also reduces the weight.

[0044] Please refer to Figure 6 (Flow rate at 9.465 L / s, existing impeller outlet pressure diagram) and Figure 7 (Flow rate at 9.465 L / s, composite impeller outlet pressure diagram). According to the existing impeller and composite impeller in the above one control experiment, in the pumplinx computational fluid dynamics software, under the conditions of the same water body, grid number, flow rate, and similar number of surfaces, the average pressure at the outlet of the pump body equipped with the composite impeller is 112.4×10 6 Pa, and the average pressure at the outlet of the pump body equipped with the existing impeller is 109.5×10 6 Pa. 112.4 / 109.5 = 102.65%, and the pressure at the outlet of the pump body with the composite impeller is 2.65% higher than that of the pump body with the existing impeller at the outlet.

[0045] Please refer to Figure 8 and Figure 9 shown. According to the existing impeller and composite impeller in the above one control experiment, in the pumplinx computational fluid dynamics software, under the conditions of the same water body, grid number, flow rate, and similar number of surfaces, the average value of the maximum impeller power of the pump body equipped with the composite impeller is 20.99 kW, and the average value of the maximum impeller power of the pump body equipped with the existing impeller is 20.92 kW. 20.99 / 20.92 = 100.33%, and the maximum impeller power of the composite impeller is only 0.33% higher than that of the existing impeller.

[0046] According to the existing impeller and composite impeller in the above one control experiment in the actual prototype test, the certification requirements of the fire pump are used as the test standard (the head at 1.5 times the flow rate of the fire pump must be greater than or equal to 65% of the head at the rated flow rate, and if it is less than 65%, the flow rate point does not meet the fire pump certification requirements).

[0047] For the existing impeller at a flow rate of 9.465 L / s (150 usgpm) and a head of 86.5 m, at its 1.5 times flow rate point of 14.2 L / s (225 usgpm), the head is 72.89 m. 72.89 / 86.5 = 84.27% > 65%, and the maximum shaft power is 22.69 kW. The existing impeller meets the fire pump certification requirements at a flow rate of 9.465 L / s (150 usgpm).

[0048] For the existing impeller at a flow rate of 12.63 L / s (200 usgpm) and a head of 77.81 m, at its 1.5 times flow rate point of 18.93 L / s (300 usgpm), the head is 50.25 m. 50.25 / 77.81 = 64.58% < 65%, and the maximum shaft power is 22.69 kW. The existing impeller does not meet the fire pump certification requirements at a flow rate of 12.63 (200 usgpm).

[0049] For the compound impeller, at a flow rate of 9.465 L / s (150 usgpm) and a head of 88.25 m, at 1.5 times the flow rate point of 14.2 L / s (300 usgpm) the head is 74.34 m, 74.34 / 88.25 = 84.24% > 65%, the maximum shaft power is 22.84 kW, and the compound impeller meets the fire pump certification requirements at a flow rate of 9.465 (150 usgpm).

[0050] For the compound impeller, at a flow rate of 12.63 L / s (200 usgpm) and a head of 78.64 m, at 1.5 times the flow rate point of 18.93 L / s (300 usgpm) the head is 54.54 m, 54.54 / 78.64 = 69.35% > 65%, the maximum shaft power is 22.84 kW, and the compound impeller meets the fire pump certification requirements at a flow rate of 12.63 (200 usgpm).

[0051] As can be seen from the above, the maximum flow rate of the compound impeller that meets the fire pump certification is 12.63 L / s (200 usgpm), and the maximum flow rate of the existing impeller that meets the fire pump certification is 9.465 L / s (150 usgpm). The flow rate range of the compound impeller that meets the fire pump certification is larger than that of the existing impeller. At a flow rate of 9.465 L / s (150 usgpm), the head of the compound impeller is 88.25 m, and the head of the existing impeller is 86.5 m, 88.25 / 86.5 = 102%. The maximum shaft power of the compound impeller is 22.84 kW, and the maximum shaft power of the existing impeller is 22.69 kW, 22.84 / 22.69 = 100.66%. Under the same flow rate condition, the head of the compound impeller is 2% higher than that of the existing impeller, and the power only increases by 0.66%.

[0052] The above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformation made using the content of the specification and drawings of the present invention, directly or indirectly applied in the relevant technical fields, is similarly included in the patent protection scope of the present invention.

Claims

1. A low specific speed non-overload centrifugal pump, characterized in that: A pump body and a composite impeller arranged inside the pump body, the composite impeller comprising an impeller rear cover plate, blades and an impeller front cover plate, the disc surface of the impeller rear cover plate is evenly provided with blades around its own axis, a fork is provided at a position 1 / 5 to 1 / 4 of the length of the inlet end of the blade toward the outlet end of the blade, the fork divides the outlet end of the blade into at least two forked blades, so that the effective flow channel area between the blades is reduced, and the flow channel inlet area between the blades is larger than the outlet area; The wrap angle of the blade on the disk surface of the impeller rear cover plate is 155° to 170°, and the outlet angle of the blade on the disk surface of the impeller rear cover plate is 15° to 19°; the thickness of the inlet end of the blade is 2.2 mm to 2.5 mm, and the thickness of the outlet end of the forked blade is 3.8 mm to 4.3 mm; The impeller front cover plate covers the blades, and a casting exhaust port is arranged on the impeller front cover plate. The casting exhaust port is arranged on the impeller front cover plate along the bifurcation, and the bifurcation blades do not pass directly under the casting exhaust port; The disc surface of the impeller rear cover plate is evenly provided with 4 to 6 blades around its own axis.

2. The low specific speed non-overload centrifugal pump according to claim 1, characterized in that: The wrap angle of the blade on the disk surface of the impeller rear cover plate is 160°, and the outlet angle of the blade on the disk surface of the impeller rear cover plate is 17°.

3. The low specific speed non-overload centrifugal pump according to claim 1, characterized in that: The thickness of the inlet end of the blade is 2.3 mm, and the thickness of the outlet end of the forked blade is 4 mm.

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